Conventionally, there have been cases where, of the materials constituting a tire, the amount of bonding is insufficient (bonded section is separated) for sheet members such as reinforcing sheet members and the like, namely, a carcass and an inner liner. In such cases, there is a risk of the tire bursting and, as such, there is a need to detect bonding defects in reinforcing sheet members prior to shipping and prevent the distribution of defective tires. In tires where the sheet members are appropriately disposed, both end portions of the sheet members faces in the tire circumferential direction, and a portion of both end portions are overlapped (bonded to each other) on the tire circumference. Thus, a structure is obtained in which the sheet members are disposed throughout the entire circumference of the tire. However, in tires where a bonding defect of the sheet member exists, only slight irregularities occur in the completed tire surface. Thus, even if inspected by a person visually or through tactile sensation, there is a high possibility that the defect will be missed.
Devices for automatically detecting such a bonding defect of sheet members are known (e.g. see Japanese Unexamined Patent Application Publication No. 2004-354258A).
In the device described in Japanese Unexamined Patent Application Publication No. 2004-354258A, to produce a pneumatic tire, a ring band-like sheet material is formed by connecting ends of a sheet member. When inspecting the bonded portion of the sheet member, the ring band-like sheet material is wound on a drum and, in this state, the drum is rotated at a constant speed. While rotating the drum, an optical displacement sensor positioned near the drum surface is used to acquire displacement signals related to sheet thickness.
Furthermore, these displacement signals are sampled on the basis of the frequency of a clock that is incorporated into an arithmetic processing mechanism of a computer device, and distance of the drum circumferential direction corresponding to the sampling interval is calculated from the relationship between the clock frequency and the drum rotation speed.
As a result, waveform data pertaining to sheet thickness of the ring band-like sheet material is generated and, in this waveform data, a point where the value of the displacement signal related to the sheet thickness begins to deviate from a predetermined range or begins to return to within the predetermined range is determined as a leading edge and/or trailing edge of a protruding region or a recessed region.
Furthermore, an irregularity region dimension in the drum circumferential direction of the protruding region or the recessed region is calculated on the basis of the determined leading edge and/or trailing edge, and a determination is made as to whether this irregularity region dimension data is within a specified range or within an acceptable range.
Devices such as that described in Japanese Unexamined Patent Application Publication No. 2004-354258A perform detection while the ring band-like sheet material is wound on the drum, and are incapable of performing detection on completed tires.